Method of applying abrasives to grinding-machines.



H. K. HITGHGOGK.

METHOD OF APPLYING ABRASIVES T0 GRINDING MACHINES.

2 SHEETS-SHEET 1.

4 11 9 1 0 1 m M d w n .m a P 2 m 1 Y A M D B n F N 0 I T A G I L P P A5 O 7 1 9 8 .1

INVENTOR H. K. HITOHOOGK.

METHOD OF APPLYING ABRASIVES TO GRINDING MACHINES.

APPLICATION FILED MAY17, 1912.

Patented Mar. 10, 1914.

2 SHEETS-SHEET 2.

47 FIG.8.

WITNESSES INVEN'I'OFI fiv I '%M zdw "To all whom it may concern:

'UMTED Es rannrnroia HALBERT K. HITCHGOCK, or TARENTUM, PENNSYLVANIA.

I METHOD or APPLY'iNG msRAsivEs T0 eaznnrne-nrienmns.

/ Specification of Letters Fatent.

Patented Mar. 10,1911.

Original application filed J'uly 31, 1911, Serial No. 641,484. Dividedand this application filed May 17,

- 1912. seria naeezsec.

Be it known that I, HALBERT K. HITCH- COCK, a residentof Tarentum, inthe county of Allegheny and State of- Pennsylvania,

have invented a new and useful Improvement in Methods of ApplyingAbrasives to Grinding-Machines, of which the following is aspecification. I

This invention relates to a method of handling, grading and applyingfinely d1- vided materialmixed with liquid, such as sand or otherabradingmaterial for use with grinding machines.

In the grinding and smoothing of material. requiring a smooth surface,such as plate glass, marble and granite, it is desirable that after theabrasives have passed between the material to be ground and the runnersor rubbing bed, the finer particles be separated from the coarser onesand saved to be used in the finishing operation and the coarserparticles returned to the grinder to assist in the roughing operations.I

The object of the present invention is to provide a methodof grading andapplying such materials wherein the supply to and withdrawal of thematerial from the grading vessel goes on simultaneously, the finermaterial during the roughing operation be ing held back for thesubsequent smoothing and finishing operation.

Further objects of the invention are to provide a method" whereby theproper ratio ot the water or other liquid to the sand or other abradingmaterial may be regulated; to provide a method which requires simplerand-less expensive apparatus than with the methods heretofore suggested;and to provide forstarting the finishing operation at any time andbringing it to a speedy close by a series of steps or jumps from acoarse to a fine grade, will .be fully described hereinafter.

In-the accompanying drawings, Figure 1 is a vertical sectional view ofapparatus for carrying out the method; Fig. 2 is a' vertical viewthrough the discharge mechanism from the primary grading cone; Fig. 3 isa plan view of the same; Fig, 4 is a transverse Vertical section on theline 44, Fig. 2; Figs. 5 and 6 are detail views showing differentpositions of the valve; Fig. 7 is an enlarged vertical sectional view ofthe valve controlling the outlet from the fie and cone; and

Fig. 8 is a horizontal section on the line 88, Fig. 7.

In my Patent No. 934,441 issued September 21, 1909, is described andclaimed a certain process for grading fine material in suspension, andin m Patent No. 934,612, September 21, 1909, have illustrated and jdescribed certain apparatus for grading material, conducting the same toa grinding apparatus and then returning it for regrad mg. I

The method of gradin or separating the material into grades of thepresent application has certain general resemblances and follows thesame broad principle as the method described in my Patent No! 934,441

above identified.

In the use of the apparatus illustrated in Patent No. 934,612, part ofthe material after being graded is deposited in tanks or bins from whichit is taken to the grinding machines as necessary or desired, and uponthe return from the grinding machines is ,re'g'raded and again depositedin such tanks to provide a method for which simpler and less expensiveapparatuscan be employed and in which a continuous uninterrupted cyclewith the abrading-material in suspension is carried on so thatthematerial can be handled at less cost and with less labor than withthe apparatus shown in my prior patent.

In the drawings I have illustrated apparatus and herein will describethe mode for grading abrading material and applying the same for glassgrinding operations, but it will be understood that certain features ofthe invention are applicable to grading materials and applying them toother purposes. f

- In the drawings 1 indicates a grinding tableprovided'with' a 'pair ofrunners 2 of the usual form. This grinding mechanism ,may be of any'kindor type and as shown is I the water and used abrading material over ascreen 5 to a pit or sump 6, from which it 'is drawn through pipe 7 bymeans of a centrifugal pump 8 driven by any suitable motor and forcedthrough pipe 9 into the bottom of the grading vessel 10. The gradingfvessel is arranged to regrade theused, and

grade thelnew, materials so as to retain all of the materlal coarserthan a given slze.

\ Thecentrifugal pump 8 forces the mixture of sand and water upwardlthrough the 'vessel 10, so that-the up owing stream therein causes thematerial to grade itself according to size upon the principle, explainedin my Patent No. 934,441, above referred to. The dirt, scummy materialand abrasive material which is too fine for furthere use escapes throughthe overflow pipe 11' toa suitable conduit or sewer 12, which alsocarries the overflow from the sump 6. The finest grade of sand in thegrading vessel 10 escapes through an outlet 13 near the top of saidvessel to the fine sand cone 14 which. is arranged in proximity to themain grader and at such a level that the fine sand 'mixed with waterflows thereto by gravity.

The fine sand collected in the cone 14 is used for the final orfinishing grinding of the glass,after the rough grinding has beeneffected by the coarser material drawn from the grading vessel 10.

The fresh abrading material or sand can be added to'the system at anypoint, either into the grading vessel 10, or directly upon the table, orin the gutter surrounding the latter. In the drawing 16 represents aclam shell bucket and 17 a conduit, either of which may be used forsupplying fresh sand to the system, such as by depositing the same in ahopper or bin 18 from which it is admitted as necessary into the vessel10, in order to replenish the supply of sand due to the loss'of aportion which becomes pulverized in the grinding operation and is washedout through the overflow 11. Any other manner of supplying fresh sand tothe system will serve my purpose equally as well.

The grading vessel 10 may be of any size or form, but preferably is ofinverted cone shape, as shown, with the side walls having such slope andthe vessel having such diameter that the several grades seek a state ofequilibrium therein at well defined strata and at the points from whichthey are to be withdrawn, depending upon the ratio of the weight of theparticles to the resistance offered to falling in the upward current ofwater, as described in my Patent No.

934,441, above identified. The action of the upward flow of water inthis conical vessel separates the material into grades, the coarsestbeing at the bottom and the successive strata decreasing in coarsenesstoward. the top. In order to separately withdraw the grades from thegrading vessel there are projected into said vessel a series of pipes21, 22 and 23, in number depending upon the grades which are to beseparately withdrawn. The lower or inner ends of these pipes are atdifferent heights in the grading vessel and each opens approximately inthe strata or zone of the grade which it is desired to withdraw throughthat pipe. These open ends are preferably arranged close to the centerof the cone and all of the pipes extend through the side of the cone atsubstantially the same level.

The outer ends of these pipes are bent downwardly somewhat, as shown,and they are arranged to discharge into spout 25 which projects over thegrinding table, preferably between the runners, and which is perforatedto discharge the mixture of sand and .Each of these operating sheaves isweighted,

as at 36,so that when closed the weight holds the valves closed againstthe head or pressure of mixture in the grading vessel, and

when opened this weight keeps the valve open. Each sheave is providedwith a rope or similar device 37 for operating the same.

Each of the valves is provided with a soft packing or face 38 arrangedto seat against the open end of the pipe and close the same. WVhen thevalves are open the mixture of sand and water is forced out of thepipes, by the pressure of the head in the cone 10, but thispressure is.not so great but "that when the valves close the pipes, the outflowimmediately ceases, but assoon as a valve is opened a flow through theopen pipe is set up. As soon as a valve is closed the sand in the pipedrops'out' of the same into the cone 10 due to the fact that there is noupward flow of water in the pipe, so thatthe sand gradually drops downuntil is escapes from the inner open end of th'e'pipe. Consequently thepipes ordinarily do not clogbut are filled with practically clear waterduring such time as the mixture, is not being withdrawn from the same.In case sand or anything else should clog in any of these pipes from anycause I have provided the following arrangement for clea'ring .the same:The outer ends of the pipes are connected to a suitable chamber' -49which is supplied. with water under pressure'throughpipe 41. Fromchamber40 a port leads to the outer end of; each of the withdrawalcommunication from chamber 40 to the de- I wardly sired one of thewithdrawal pipes, the valves 27, 28 and 29 are each provided with aprojection or prong 44 of sufiicient lengthvto contact with itsrespective check valve--42 and lift the latter from'its seat wheneverthe. rubber facing or packing 38 is compressed. In the normal conditionof the closed valve (Fig. 2) the projection or prong 44 barely contactswith the valve 42 but does not-lift the same from its seat. Should, forany cause, one of the withdrawal pipes become clogged the rope 37 forthe valve of that particular pipe is pulled upon in a direction toforcibly compress the packing 38, which permits the prong 44 to lift thecorresponding valve 42 from its seat (Fig. 5), Water under pressure fromthe supply pipe 41 now flows inand downwardly through the clogged pipeand clears the. same of the ob struction.

Inasmuch as each of the valves 27, 28 and 29 is independently contfolledthis permits of the withdrawal of the several grades separately andindependently and to any extent or degree. In other words, it is notnecessary to withdraw all of-the grades lying between any two planesbefore taking out or beginning to take out an upper or finer grade. Thisenables the finishing operation to be brought to a speedy conclusion,whereas with prior apparatus where. the different grades were withdrawnthrough a common outlet, it was necessary to entirely withdraw all bfthe grades before the finest could be taken out. With the newarrangement the. withdrawal through any one pipe can bev stoppedwhenever desired and any one of the higher pipes opened. This enablesthe material to be withdrawn in a series of steps or jumps and enablesthe finishing operation to be started at any time and to be brought to-aspeedy conclusion.

The grading of the material in the vessel 10 goes on simultaneously withthe discharge of the graded material therefrom, the supply of ungradedmaterial being continuously forced upwardly from the bottom of saidvessel from the sump 6, as it comes from the grinding table.

In the application of abrading material,"

and particularly for grinding and smooth-v ing plate glass, it isadvantageous to vary the amount of water mixed-with the sand of thedifi'erent grades. With the coarser grades a small ratio of water canprofitably be used, while with the finer grades the ratio of waterpreferably should increase. In the apparatus illustrated the regulationof the ratio of water and sand for the different grades isautomatically. effected by propfiner grades. r

The fine sand cone 14, as heretofore point- I ed out, receives itssupply from the top stratum ofthe grading vessel 10. The sand from thisfine sand cone is withdrawn only at the end of the grinding operation,to effect the finer or finishing grinding operation. The fine sand incone 14 is'also preferably graded therein by an upward current of waterwhich is introduced into the bottom of the cone, such as through pipe 47which projects down centrally in said cone and which is open at itslower end. This pipe has a supply connection 45. ,The surplus waterescapes through the overflow 49 and prefer ably goes to the gutter 3.The eu'ect of this is to further grade the fine sand in the cone 14,bringing the coarser sand at the bottom and gradually increasing infineness toward the top so that when withdrawn through the bottomdischarge orifice 50 to the spout. 25 the finishing sand graduallybecomes finerand finer. The discharge orifice 50 of the fine sand'coneis controlled by a valve 51 secured to astem 52g'uided in the lower endof tube 47, said stem being fluted or grooved, as

.at 53, so that it can not stop the flow of water from the pipe 47Connected to the valve stem 52 is a rod 54 extending upwardly above thecone and connected to one end of lever 55 fulcrumed at 56 and havingconnected to its opposite end an operating rod 7 I 57. By pulling downon the latter the valve 52 is lifted to open the discharge orifice, andthe fine sand and water escapes to the grinding table.- e 4 In carryingout the method the sand is deposited in the vessel 10' or other suitablepoint in the system. from the clam shell bucketlfi or other source andsufiicient water is supplied, such. as through pipe 59 supplying astream of water tolwash the sand out of hopper 18. The water. mixed withsandis graded and suppliedto the grinding table and returned therefromto the grading The particles of sand move in the stream of \vatenuntilthey reach a state of equilibrium, which depends upon the ratio of thehorizontal area and wetted surface of the particles of sand to theweight thereof. Inas much as the weight varies according to the cube ofthe dimensions of the particles while the horizontal projection andwetted surface vary merely as the square ofthe same dimensions, itnecessarily follows that the larger and coarser particles drop to alower point in the upwardly flowing stream of water than do the smallerparticles. "As a consequence, the sand particles are accuratelyseparated into several grades or sizes. These grades vare withdrawnseparately and con ducted separately to the grinding table by openingthe appropriate valve 27, 28 or 29 controlling the several withdrawalpipes from said cone.

The sandand water from the grinding table finds its way to the sump 6whence it is again lifted into the grading vessel by the centrifugal pum8. 'On the grinding table more or less'of the 'sand is pulverized tosuch" a degree as to incapacitate it for further service as an abrasive.Such-fine particles escape through the overfiow 11, while the coarserparticles are again regraded and withdrawn. The .several grades arewithdrawn from the vessel 10in succession, beginning with the coarsestand continuing through thevarious grades to the finest. The capabilityof separately withdrawing the several grades from said vessel enablesthe change from one grade to another to be made at'any time and therefore made as soon as the surface of the glass is in condition to receivea finer grade. As soon as the glass is sufficiently smooth, the supplyof material from the cone 10 is discontinued, and the finishing grindingis effeeted by withdrawing the sand from cone 14, which is eifected byopening the. discharge opening 50 in its bottom. The material from thiscon'eis taken out from the bot- .tom, thereby taking outthe coarestgrades first, the material becoming finer and finer the longer thegrinding continues. During I all of the grinding with the exception ofthe I final finishing there is a continuous circulation of abradingmaterial and water from the cone 10 to the grinding table, thence to.

sump 6 and back again into cone 10. The material too fine for furtheruse is washed by the overflow into the sewer and the finest usable gradeescapes from the upper stratum in cone 10 to cone 14 for the finalfinishing operation. To compensate for these withdrawals from the systemfresh material and water are added to the system from time to time. Thesimultaneous grading and discharge from the grading vessel permits ofthe use of much smaller and less expensive vessels or conesthan withprior forms. of apparatus.

f This'application is in part a division of my application Serial No.641,484, file-:l July 31, 1911. I

What I claim is: 1. The method of applying abrasives t0 grindingmechanism, which consists in supplying the ma-terial in suspension in aliquid to avessel and therein separatingthe same into grades,simultaneously therewith withdrawing the grades from said vesselseparately and independently and conducting-the same directly to thegrinding mechanism, and also simultaneously drawing ofi from saidvesselthe finer material for use in the subsequent smoothing andfinishing operation.

. 2. The method of applying abrasives to grinding and smoothingmechanism, which consists in conducting the material mixed with' aliquid to a vessel and therein .-separating the same into grades, andsimultaneously therewith withdrawing said grades from said vesselseparately and conducting the same tothe grinding mechanism.

3. The method of applying abrasives to grinding and smoothing mechanism,which consists in conducting the material mixed with a liquid to avessel and there separating the same into various grades, withdrawingsaid several grades separately and conducting each separately directlyto the grinding mechanism, and reconducting the -used material mixedwith a liquid to said grading vessel and regrading the same there in,the grading, regrading, and circulation being carried on in anuninterrupted cycle with the material constantly mixed with the liquid.

4:. The method of applying abrasives .to grinding and smoothingmechanism, which consists in conducting the material mixed with aliquid'to a vessel and there separating the same into variousgrades,-and simultaneously therewith withdrawing said grades separatelyand in any desired sequence from said vessel, and conducting the samedirectly to the grinding mechanism.

5. The method of applyin abrasives to grinding and smoothing mec anism,which consists in conducting the material mixed with a liquid to avessel and there separating the same into various grades, withdrawingsaid grades separately and in. any desired sequence and conducting thesame in said sequence. to grinding mechanism, and reconducting the usedmaterial mixed with the liquid to the grading vessel and regrading thesame therein, said grading, regrading 521% separate grades from near thebottom of the tank and conducting the same directly to the grindingmechanism.

7. The method of applying abrasives to grinding and smoothing mechanism,consistvith aliquid and when so mixed. conduct- 9/i{ig in holding theabrasive constantly mixed 2 ing same into a tank havingdownwardlyconverging sides and therein separating the same into grades,simultaneously therewith eliminating the surplusliquid and some of thefiner material from the upper portion of the tank, and alsosimultaneously therewith withdrawing coarser material in single separategrades from near the bottom of the tank and conducting the same directlyto the grinding mechanism.

8. The method of applying abrasives .to

grinding and smoothing mechanism, consisting in conducting the abrasivemixed with water into a tank and therein separating the same intogrades, eliminating the surplus water and some of the finer materialfrom the upper portion of the tank, withdrawing coarser material'insingleseparate grades from near thebottom of the tank and conducting thesame directly to the grinding mechanism and returning the used material.from the grinding mechanism'to the tank, all such operations goingonsimul taneously.

9.. The method of applying abrasives togrinding and smoothingmechanism,- con.

sisting conducting the abrasivemixed with water into a tank andthereinseparating the same into grades, eliminating the surplus water and someof the finer material from the upper portion of the tank, andsimultaneously with theadmission of ungraded material and theelimination of the surplus water withdrawing material separately and--from any desired level in'said tank and con ducting vthe same directlyto the grinding mechanism.

10. The method of grading andapplying abrading material, consisting inseparating the same into diflerent grades, conducting the same in astate of suspension to grinding mechanism, and regrading the usedmaterial, such grading, regrading and circulation being carried on inanuninterrupted cycle with the material constantly mixed with a liquid.

11. The methodof grading and applying abrading material, consisting inseparating the same into different grades, conducting the same in astate of'suspension to grinding mechanism, and regrading the usedmaterial, such grading, regrading and circulation being carried on inan-uninterrupted cycle with the material constantly mixed with a liquid,and simultaneously with the regrading adding fresh material to saidcirculation.

12, The method of grading and applying abrading material, consisting inseparating the material into different grades, conducting the gradedmaterial mixed with a. liquid to grinding mechanism,'and regrading allof the used material above a certain size, such grading, regrading andclrculation being carried on with the material constantly mixed with aliquid.

13. The method of grading and applying abrading material, consisting inseparating the material into difi'erent'grades, conducting the gradedmaterial mixed with a liquid to a grinding machine, withdrawing fromsuch circulation the material below a certain size and the surplusliquid, adding to thecirculation fresh material to replace thatwithdrawn, and regrading all of the used material above a certain size,such grading, regrading and circulation being carried on with thematerial constantly mixed with a liquid. a

14. The method of applying abrasives to grinding and smoothingmechanism, consisting in introducingt-he abrasive into a tank,maintaining in said tank an upward flow of water, eliminating thesurpluswater and some of the finer material from the upper portion of the tank,and simultaneously therewith withdrawing the material as required, thevarious gradesbeing withdrawn independently from different levels, andconducting the same to grinding mechanisna. r

15. The method of applying abrasives'to I grinding and smoothing'mechan'ism, consisting in taking'the abrasive mixed with water comingfrom the grinding mechanism and conducting the same into a gradingvessel, grading the same therein, and simultaneously with theintroduction of the mixture into said vessel withdrawing the material asrequired, the various-grades being withdrawn independently and "fromdifier-Y ent levels therein, and reconducting the same to said grindingmechanism.

16. The method of applying abrasives to grinding and smoothingmechanism, consisting in introducing the material into a vessel with aliquid and therein producing a downward flow or travel of the materialrelative to the liquid to thereby separate it into several differentgrades, and simultaneously therewith withdrawing the material asrequired, the several grades being withdrawn from said vesselindependently "and from difi'erent levels therein, and conducting thesame to grinding mechanism.

17. The method of applying abrasives to grinding mechanism, consistingin projecting a stream of liquid vertically at a decreasing speed in asuitable vessel or tank and introducing into said vessel the abradingmaterial, and thereby separating the latter into different grades,eliminating the surplus liquid and some of the finer material'from theupper portion of the tank, and simultaneously therewith withdrawing thematerial as required, the several grades being withdrawn independentlyand from different levels therein, and conducting the same to grindingmechanism.

18. The method of applying abrasives to grindingmechanism consisting inconducting the abrasive mixed with 'a' liquid into a vessel andproducing in said vessel a downward flow or travel of the materialrelative.

to the liquid and thereby separating the material into grades,withdrawing the finer material from the upperstratum of said f vessel toa second vessel, simultaneously with the introduction of the materialinto said first named vessel separately withdrawingthe several-gradestherefrom as required and conducting the same tothe grinding mechanism,producing an upward flow of liquid relative to-the' material in thesecond named vessel and thereby grading the material therein,v andfinally withdrawing the material from said second named vessel.

. 19. The method of applying abrasives to grinding mechanism, consistingin projecting upwardly into a vessel a stream of a liquid mixed withabrasives thereby producing a decreasing flow upwardly and separatingsaid material into grades, withdrawing the coarser grades from saidvessel independentl and from difl'erent levels thereof and con uctingthe same to grinding mechanism, withdrawing the finer grades from theupper stratum of said vessel to a second vessel and therein producing anupward flow of a liquid relative to' the material to thereby grade thematerial in said second vessel, and finally withdrawing the gradedmaterial from said second vessel and conducting the same to the grindingmechamsm. 1

20. The method of applying abrasives to grinding mechanism, consistingin projecting upwardly into a vessel provided with converging walls astream of a liquid mixed with abrasives thereby producing a decreas- 1ing flow upwardly and separating said material into grades, withdrawingthe coarser grades from said vessel independently and from differentlevels therein and conducting the same to grinding mechanism, withdrawmgthe finer grades from the upper stratum of said vessel to a secondvessel and therein producingl an upward fiowofa liquid relative to t ematerial to thereby grade the material in said second vessel, andfinally withdrawing the graded material from said second vessel andconducting the same to the grinding mechanism,returning the material 22The method of applying abrasives to grinding mechanism, which consistsin-"conducting the abrasive mixed with a. liquid first to the grindingmechanism and then to a grading vessel or tank, and there separating thecoarse material and'conducting the same back to the grinding mechanism,while at the same time holding some of the finer grades still mixed withthe liquid in the grading vessel or tank, and subsequently conductingsome of the finer grades to the grinding mechanism.

23. The method of applying abrasives to grinding mechanism, whichconsists in conducting the abrasive mixed with a liquid first to thegrinding mechanism and then to a grading vessel or tank, and thereseparating", the coarse material and conducting the same back to thegrinding mechanlsm,

'while at the same time holding the finer grades still mixed with theliquid in the grading vessel or tank, separating the finer material intogrades, and subsequently conducting the finer grades in any desiredsequence to the grinding mechanism.

24. The method oit' applying abrasives to grinding mechanism, whichconsists in connoting the abrasive mixed with a liquid first to thegrinding mechanism and then to a grading vessel or tank, and thereseparating the coarse material and eliminating the surplus liquid andthe material too fine for use, conducting'the coarse material back tothe grinding mechanism,and simultareously holding some of the finergrades in suspension in the liquid in. the grading vessel or tank.

25. The method of applying abrasiv s to grinding mechanism, whichconsists in conducting the abrasive mixed with a liquid first to thegrinding mechanism and thefi to a grading vessel or tank, and thereseparating the coarse material, and eliminating Y the surplus liquid andthe material too fine for use, conducting the coarse materlal back tothe grinding mechanism,simultaneously holding some of the finer gradesin suspension in the liquid in the grading vessel or tank, andsubsequently conducting some of the finer grades to the grindingmechanism.

26. The method of applying abrasives to grinding mechanism, whichconsists in conducting the abrasive mixed with the liquid to thegrinding mechanism, collectmg the drainage therefrom and conductingthesame toand introducing the same into a primary grading vesselcontaining a relatively deep body of the-abrasive mixed with the liquidand there subjecting the particles of the abrasive to an upward movementofthe liquid relative to the movement of the. abrasive, whereby theabrasive is stratified in the liquid, withdrawing the coarse materialfrom near the bottom of the vessel and conducting the. same to thegrinding mechanism, withdrawing the fine material from near the upperportion of the primary grader to a secondary grader while at the sametime holding the intermediate grades still mixed with the liquid in theprimary grader, and after the rough grinding operation, is finishedwithdrawing the desired finer grades fromthe primary grading vessel tothe grinding mechanism.

27. The method of applying abrasives to grinding mechanism, whichconsists in conducting the abrasive mixed with the liquid to thegrinding mechanism, collecting the drainage therefrom and conducting thesame to and introducing the same into a prlmary grading vesselcontaining a relatively deep body of the abrasive mixed with ishedwithdrawing the desired finer grades 'from the primary grading vessel tothe grinding mechanism, and subsequently conducting fine material fromthe secondary grader to the grinding mechanism.

28. The method of applying abrasives to grinding mechanism, whichconsists in conducting the abrasive mixed with a liquid first tothegrinding mechanism and then to a grading'vessel or tank containing arelatively large, deep body of the abrasive mixed with the liquid, andthere separating the same into a series of grades, and while grading theabrasive materialconducting the coarse material from said vessel or tankdirectly at the grinding mechanism and the fine material to a secondarygrading vessel, and maintaining the intermediate grades suspended in theprimary grading vessel.

29. The method of applying abrasives to grinding mechanism, whichconsists in conducting the abrasive mixed with the liquid to thegrinding mechanism, collecting the drainage therefrom and conducting thesame to and introducing the same into a primary grading vessel or'tankbelow the surface of the liquid therein, there separating the same intoa series of grades, conducting the coarse material from said vessel ortank directly to the grinding mechanism, withdrawing the fine materialfrom the primary grading vessel at a level above the inlet thereto andconducting the same to a. secondary grading vessel, and after the roughgrinding operation is finished conduc-ting'some of the finer materialfromthe secondary'grading vessel or tank to the grinding'mechanism.

30. The method of applying abrasives to grinding mechanism, whichconsists in conductingthe abrasive mixed with the liquid firstto thegrinding'mechanism and then to a primary grading vessel or tank andintroducing the same thereinto below the surface of the liquid therein,separating the abrasive into a series of grades and simultane ouslyconducting the coarse material to the grinding mechanism, withdrawingthe fine material from the primary grading vessel or tank at a levelabove the inlet thereto, and maintaining the intermediate gradessuspended inthe primary grading vessel or tank. v a

p 31. The method of applying abrasives to grinding mechanism, whichconsists in conducting theabrasive' mixed with the liquid drainagetherefrom and conducting the same to and introducing the same below thesurface of a large, deep body of the material mixed with the liquid,there separating the material into grades, and simultaneouslywithdrawing the coarse material and conducting the same, directly to thegrinding to the grinding zmechanism, collecting the uid and conductingthe same to'a secondary grading vessel.

33. The method of applying abrasives to rinding mechanism, whichconsists in coni ucting the abrasive. mixed with the liquid I to thegrinding mechanism, collecting the drainage therefrom and conducting thesame to and introducin grades, withdrawing the fine material from saidgrading vessel at a level above, the inlet thereto and introducing thesame into a sec- 11 ondary grading vessel or tank, and withdrawing thecoarse material from near the bottom of the primary grading vessel orftank and conducting the same directly to thegrinding mechanism.

34. The method of applying abrasives to inding mechanism, which consistsin conucting the abrasive mixed with the liquid to the grindingmechanism, collecting the drainage therefrom and conducting the same toand introducing the same below the surface of a large, deep terial mixedwith the 11 uid in a primary grading vessel or tank, eliminating thesurplus liquid and the material too. fine for use from said gradingvessel or tank and separating the rest of the material into a se ries ofgrades, withdrawing the fine ma-,;' terial from sald grading vessel arelevel above the inlet thereto and introducingthe same into asecondarygrading vessel or tank,.withdrawing the coarse'material from Ianism.

35. The method of applying abrasivto' near the bottom of the primarygrading vessel or tank and QOIldllCtlIIg the same directly to thegrinding mechanism, and after the rough grinding operation is finishedconducting 'the fine material from the secondary grading vessel or tankto the grinding mechbody of the ma-' inding mechanism,'which consists inconc uctlng the abrasive-mixed with a liquid to the grinding mechanism,collecting the drainage therefrom and conducting the same to andintroducing the same into a vessel and there increasin 'the proportionof the abrasive material re ative to theliquid and separating the.material into grades, and re-' conducting the condensed rades from saidvessel to the grinding mechanism.

36. The method of applying abrasives to rinding mechanism, whichconsists in conducting the abrasive mixed with aliquid to the grindingmechanism, collecting the, drainage therefrom and conducting the same toand'introducing the same into a vessel or tank,-'withdrawing the coarsermaterial and reconductingi' the same to the grinding mech anism, andsimultaneously increasing the proportion of the finer material relativeto the liquid and maintaining the condensed I mixture in suspension inthe liquid in' said vessel or tank.

'37. The'method of appl ing abrasives to grinding mechanism, whicconsists in conacting the abrasive mixed with a liquid to the grindingmechanism, collecting I the drainage therefrom and conducting the 'sameto and introducing the same intoa vessel .or tank, withdrawing thecoarser material and reconducting the same to the grinding mech- 'anism,simultaneously increasing the-pro- ',p0rti0n of the finer materialrelative to the liquid and maintaining the condensed mixture insuspension in the li uid in saidvessel or tank, and subsequent ywithdrawing 30' I the condensed finer dgrades and conducting the same tothe grin ng mechanism.

In testimony whereof, I have hereunto'set my hand.

, HALBERT K. HITCHCOCK. Witnesses; v

WM. P. LARKIN,

WILLIAM B. WHARTON.

